Process for making intermediates for producing basic compounds



Patented Oct. 14, 1952 PROCESS FOR MAKING INTERMEDIATES BASIC COMPOUNDS Charles C. Price, South Bend, Ind., and Royston FOR PRODUCING M. Roberts, Austin, Tex.,

assignors to the United States of America. as represented by the Secretary of the Army No Drawing. Original application March 1, 1946,

Serial No. 651,432. Divided and this application March 10, 1950, Serial No. 149,014

The present invention relates to formamidines and more particularly to a new and improved method of converting diarylformamidines to certain beta-arylaminoacrylates or 'their corresponding isomeric anils foruse'in the synthesis of e-hydroxyquinoline compounds.

These may be used for the preparation of 4- chloroquinolines which in turn may react with substances containing the hydroxyl, sulfhydryl or amino group to form quinolines containing an ether, thioether or amine group at position four. A number of compounds of the latter type are of value as antimalarial drugs (see, e. g., Andersag, Breitner and Jung, U. S. Pat. No. 2,233,970) and their preparation as disclosed utilizes a 4-chloroquinoline intermediate.

As pointed out in the pending application of Price, Roberts and I-Ierbrandson, Ser. No. 597,584, filed June 4, 1945 (Invention Disclosure OSRD- 3834), beta-phenylaminoacrylates of the type I, or their corresponding isomeric anils I-A where X is a nuclear substituent and Y is acarbalkoxy group (-COO-R.) a cyano group (-CN or a carbanilino group (--CONHAr) may be cyclized under appropriate conditions to form substituted 4-hydroxyquinoline compounds'of the type (II). g

The preparation of aminoacrylates (I or LA) above has been accomplished previously by condensation of ethoxymethylenem'alonic esteror ethoxymethylenecyanoacetic ester with arylamines (Claisen and Haase,;Ann., 297, 75 (1897) Gould and Jacobs, Jour. AmenChem. Soc., 61, 2890 (1939); Price, Roberts andHerbrandson) to give I with Y COOR. or ON by condensation of diarylformamidines with active methylene compounds (Dains, Malleis and Myers, Jour. Amer. Chem. Soc., 35, 970 (19.13); Snyder and Jones, U. S. Applications Nos. 597,586 and 597,587, filed June 4, 1945, O'SRD Disclosure Nos. 3835 and 3836 to giveIwith Y=CNorCONHAr.

The cyclized products (II) may be hydrolyzed 4 Claims. (Cl. 260-471) to the corresponding 'carboxylic acids (III) and the latter readily decarboxylated to form the 4- hydroxyquinoline compounds of the type (IV),

the latter being useful as intermediates in the preparation of certainrcornpounds of high antimalarial activity (Andersag, Breitner and Jung).

COOH 7 I X X l I C N v v in I 1v 7 g The conditions necessary to effect the cyclization step in the foregoing synthesis dependupon the nature of the Y group present in the starting materials (I or I-A). In the case where Y is a carbalkoxy group (*COOR), cyclization of (I) or (I-A) to form (II) is readily accomplished in high yields merely by heating the diester, either by itself or in solution or suspension in a suitable high boiling heat exchange medium or solvent, to a temperature of the order of about 250 C.

However, in the case of the cyano compounds (i. e., Y=-CN in I or I- -A) or of the carbanilino compounds (i. e., Y=CONHAr in I or I-A), cyclization requires the use of a very large proportion of reaction solvent (i. e., high-dilution) during the heating step, in order to obviate the production of a tarry reaction product. 7 For this reason,

the diester compound (Y=COOR in I or I-A) constitute somewhat more satisfactory starting materials than the corresponding-cyano orcarbanilino compounds.

The group Y in I is of importance when the group X in the aryl residue is such that cyclization may proceed to form two isomers. For example, when X is a chlorine atom in the meta position, cyclization may result in the appearance of the chlorine atom in either the 5- or 7- position of the resulting quinoline. When Y is a negative group, such as COOR, CN or CONHAr. the proportion of the undesirable 5-isomer is very small. On the other hand, cyclization of simple beta-(m-chloroanilino) -acrylates (Y=H in I) (Price and Reitsema, U. S. Application No. 597,585, filed June 4, 1945, OSRD Disclosure No. 3850) or of beta-carbethoxy-beta-(m-chloranilino) acrylates (Surrey and Hammer, Jour. Amer. Chem. Soc., 68, 113. (1946) produces a considerable proportion of the5-isomer.

The conditions necessary to bring about the hydrolysis of the cyclizedproduct '(II) to thecor responding .carboxylic acid (III) also {depend For the reasons indicated above, other things being equal, the diesters (Y=COOR in I or I-A) represent the most attractive starting materials for the synthesis of various -hydroxyquinoline- 3-carboxylic acids or their derivatives in accordance with the method indicated. However, for large scale applications, the use of these diesters (Y=COOR in I or LA) in the preparation of quinoline compounds has heretofore been restricted because of the limited availability of the raw materials necessary for the synthesis of the diesters in accordance with the best prior art method (i. e., condensation of the appropriate aniline compounds with ethoxymethylene-malonic ester). Furthermore, the use of ethoxymethylene malonic ester on a commercial scale is objectionable for the additional reason that its pronounced skin-irritant action necessitates extreme handling care to prevent incapacitation of operating personnel. It was therefore evident that the utility of the above described Price, Roberts and Herbrandson synthesis could be greatly increased, particularly insofar as large scale applications were concerned, provided the diester starting materials (Y=COOR in I or I-A) could be prepared by an improved process which did not involve the use of ethoxymethylene malonic ester as an intermediate.

Broadly speaking, the object of the present invention is to provide a new and improved method of synthesizing 2-N-arylamino-1-carbalkoxyacrylic esters of the type (V) or their corresponding isomeric anils (VI) ArNH-CH=C(COOR) 2 V ArN=CH- CH(COOR) 2 VI bya process that is readily adaptable to large scale manufacture and which starts with readily available raw materials. For purposes of convenience these compounds will hereinafter sometimes be referred to as arylaminomethylenemalonic esters," this term being understood to include the isomeric anils (VI).

A more specific object is the provision of an improved synthesis of compounds of the type (VII) and (VIII) NII-CH=C(C O O R),

VII

N=CHCH( C O RM VIII method of synthesizing 7-halo-4-hydroxyquinoline compounds or the type (IX), (X) and (XI) and the 4,7-dihaloquinoline compounds of the type ()HI) on on j c o o R f o o o n X \N X N/ IX x on 71 f] q x- X- XI R being an alkyl group and X a halogen group such as fluoro, chloro, bromo or iodo.

Other objects and advantages of the invention will be apparent as the description progresses. The foregoing objects may be accomplished in accordance with the present invention, which is based upon the discovery that, under the proper conditions to be described later, thereaction between a diarylformamidine (XIII; Ar=aryl) and a malonic ester (XIV; R=alkyl), may be controlled to produce the diester (XV, or its corresponding anil) in good yields, rather than the amide-ester or half-ester (XVI, or its corresponding anil) that is reported to constitute the only reaction product formed from these reactants under all conditions heretofore employed (cf. Dains, Malleis and Meyers, Jour. Amer. Chem. Soc., 35, 970 (1913)).

ArNHCH=NAr XIII ArNHCH=C(COOR)2 CH2 COOR) XIV AI'NH-CH=C(COOR) CONHAI XVI Inasmuch as the diarylformamidines ()HII) are readily obtainable in high yields from formic acid and the appropriate aryl amine, the process of the present invention provides an excellent synthesis of arylaminomethylenemalonic esters (XV), generally, and of the starting materials (Y=-COOR in I or LA) used in the Price, Roberts and Herbrandson synthesis of 4-hydroxyquinoline compounds, in particular.

In carrying out the process of the present invention, a reaction mixture containing roughly equimolar proportions of the selected diarylformamidine (XIII) and the malonic ester (XIV) is heated to a temperature and for a time merely suflicient to produce the diester (XV) but insufficient to cause the formation of substantial quantities of the amide-ester (XVI). In other words, the time-temperature relation is so adjusted that the reaction is substantially stopped at the diester stage (XV) rather than the amide-ester or half-ester stage (XVI). In short, the invention is based upon the discovery that the time-temperature relation for the reaction between a diarylformamidine and malonic ester determines the course of the reaction.

Generally speaking, if the reaction mixture is heated from about 2 to about 6 hours at a temperatureof about C. to about C., the reaction products consist predominantly of the diester (XV) and the liberated .arylamine (ArNI-Iz); only a small proportion of the halfester (XVI) is formed under these conditions by the interaction of the firs't-stage'reaction prodnote. If on the other hand the reaction condition inthe high boiling solvent to a temperature tions are significantly more strenuous as regards of the order of 250 C. Under these conditions, either the time or the temperature of the reacboth the diester and the half-ester will cyclize tion, the reaction product consists predominantly in good yield: the solution, although relatively of the half-ester or ester-amide (XVI). Thus. concentrated'in respect to the diester, is rela-g for example, in the case of the formamidine of tively dilute in respect to the amide-ester, and m-chloroa'niline and 'diethylmalonate, if the retherefore the amide-ester as well as the diester action mixture is heated for three hours at 135 cyclizes to the corresponding quinoline com- C., the reaction proceeds in large measure to the pounds. The cyclized reaction product thus obamide-ester stage (XVI), whereas if the same tained, consisting of the quinoline carboxylic esmixture is heated for the same time at 115-125 ter and a minor proportion of the correspond- C., an excellent yield of the diester (XV) will be ing anilide may be'treated with hot aqueous alobtained. kali, which, as previously explained, readily sa- The reaction mixtureproduced by the process ponifies the ester but leaves the corresponding of the present invention may be worked up in anilide unchanged. The difierence in the revarious ways dependinglargely on the use to activity of the ester and the corresponding anilide which the product is subsequently put. Where it therefore provides a convenient method for their isdesired to produce diester (XV), substantially separation the anilide may be filtered from the free ofcontamination with the half-ester (XVI), alkaline solution and the latter acidified to libthe reaction mixture may be worked up by seperate the free acid (X). If desired, the unhydroarating the reaction products and the unrelyzed anilide compound thus recovered may be acted starting materials, using any appropriate converted to the acid (X) by treatment with hot procedure and then recovering the diester by 75% aqueous sulfuric acid; as a result of this excrystallization from a suitable solvent. pedient, the by-product (half-ester) of the main One method of isolation that has been found preparative reaction is usefully employed to augespecially satisfactory is to dissolve the reaction ment the yield of acid, yet special precautions mixture inawater-immiscible solvent (e. g.,benregarding dilution during cyclization are not zene) and then to treat the solution with aquenecessary because of the minor extent to which ous hydrochloric acid. This treatment results in the half-ester is produced in the formation of the the precipitation of the hydrochloride of any undiester by the process of the present invention. reacted formamidine and the latter may readily In order more clearly to disclose the nature of be separated from the two liquid layers. The the p nt v o W Specific D S,' aqueous liquid layer contains the hydrochloride lustrating preferred applieetien Ofthe p isalt of the aniline compound liberated in the rep c sse above, Wi l hereinafter be described action (AIfNI-IaI-ICI) and this may be recovered if in considerabledetail. It should be clearly undesired by evaporation of the aqueous solution to de stcod, however, that these exampl e p edryness or by other means. The non-aqueous sented solely for the purposes of illustration; they g, benzene) layer c t i th di te (XV are not intended either to delineate the scope of excess malonic ester, any half-ester (XVI) as theinvention to limit e ambit f the pwell as the non-aqueous solvent used for cyclizapended claims. tion. The volatile components of this mixture 40 I EXAMPLE I I (benzene, malonic ester and a small amount of Y alcohol in some cases) may be recovered by dis- The reeetlons dm v be p s t d y tillation, and the residue, consisting of the diesthe followmg m V ll6-l20 o.

(E) s (B) oo15-o-o5ri, 250 0. l

mClC5H4NH-CH=C ONHC6H4C1-lll 0211.011

(F) NaOHl CaH5O CaH5lv250 OH OH 00011 CONHCdHlCl-III N N (0),. (D) ter and perhaps a small amount of the amide- In this example, ethyl-a-carbethoxy-p-mester, may be readily purified by crystallization -chlorophenyl-formamidine (E). obtained from from a suitable solvent (e. g., ether, petroleum diethyl malonate and di-m-chlorophenyl-formether). amidine (A), was isolated by extracting the hy- If the diester (XV) produced by the process drochloric acid-acidified reaction mixture with a of the present invention is to be employed in the volatile, Water-immiscible solvent (e. g., benzene) synthesis of e-hydroxyquinoline compounds, the after which the diester was separated by distillaseparation' of the diester from any contaminattion of the volatile components, of the solution.

ing half-ester need not be carriedout prior to The diester thus isolated was then dissolved in a the cyclization step; for the crude material obnon-volatile solvent (diphenyl ether) and the sotained as described above, or by the useof'a high lution heated to a high temperature to effect, boiling water-immiscible solvent (e. g., diphenyl 'cycllzationr Thereafter the resulting phenyl -ether) in lieu of benzene, may be heated in solu- 7 ether solution was directly treated with hotaqueous alkali to saponify the quinoline-3-carboxylic acid ester present in the solution. The aqueous alkaline solution was then separated from the diphenyl ether solution and the former acidified to liberate the free quinoline-3-carboxylic acid (C).

(a) PREPARATION OF THE DIESTER In a 50-cc. Erlenmeyer flask were placed 13.3 g. (0.05 mole) of di-m-chlorophenylformamidine and 8.0 g. (0.05 mole) of diethyl malonate. The flask was heated in an oil bath at 116-l20 C. (inside temperature) for three and one-half hours. To the reaction mixture was then added 20 cc. of aqueous hydrochloric acid and 10 cc. of benzene. The insoluble hydrochloride of unchanged di-m-chlorophenylformamidine which precipitated was collected by vacuum filtration after themixture had been shaken vigorously. An additional cc. of benzene was added to the filtrate, the mixture was transferred to a separatory funnel, and the layers were separated. The aqueous solution was extracted with an additional -cc. portion of benzene. The combined benzene extracts were washed with 20 cc.

oi. water, which was then added to the main aqueous acid solution (Note 1).

The benzene solution was distilled at atmospheric pressure and finally at reduced pressure (Note 2). To the residue was added 10 cc. of ether and 25 cc. of low boiling petroleum ether and the solution was cooled in an acetone-dry ice mixture. After one and one-half hours the mixture was filtered and 6.3 g. (Note 3) of very fine white needles were collected; M. P. 48-49 C. This product was shown to be ca. 90% of the diester (Arzzm-chlorophenyl in XV) and ca. 10% of the corresponding half-ester (Ar mchlorophenyl in XVI), this being established by (l) recrystallization and (2) cyclization. Hence, the yield of the pure diester was about 38%, neglecting the starting materials recovered.

(b) RECRYSTALLIZATION OF THE PRODUCT A 1.0-g. sample of the product was recrystallized from 12 cc. of 95% ethanol. The crystals recovered amounted to 0.10 g. and melted at l02-103 C. A second recrystallization from 5 cc. of ethanol brought the melting point to 112-113 C.; mixed melting point with an authentic sample of ethyl-a-m-chlorocarbanilido-,8-m-chloroanilinoacrylate (Ar in XVI m-chlorophenyl was 112-113 C.

Th filtrate from the first recrystallization was evaporated to dryness at room temperature and the residue was recrystallized from 10 cc. of low boiling petroleum ether to give fine white needles, M. P. 53-54 C.; mixed melting point with an authentic sample of ethyl-a-carbethoxy-o-mchloroanilyinoacrylate (Ar in Xvzm-chlorophenyl) was 53-55 C.

(c) CYCLIZATION, HYDROLYSIS AND DECARBOX- YLATION A 3.0-g. sample of the crude product obtained from (a) was melted, added to 9 cc. of boiling diphenyl ether in a 50-cc. round-bottomed flask, and washed in with another cubic centimeter of hot solvent. The crystals which separated after three or four minutes soon filled the mixture, and the heating was only continued fifteen minutes. On cooling, the reaction mixture set to a solid light yellow mass. To this was added 10 cc. of 10% sodium hydroxide solution and the mixture was heated under reflux for twenty minutes. When the two-phase liquid mixture cooled, a precipitate appeared in the aqueous layer; this was 8 collected by filtration and amounted to 0.3 g. It melted at 290-305 C. (uncor.) and consisted of 3 m chlorocarbanilido 4 hydroxy 'I chloroquinoline (Xz'Z-chloro; Yzm-chlorocarbanilido in II) Ether was added to the filtrate and the layers were separated. The aqueous layer was extracted with another 10-cc. portion of ether and then neutralized with 10% hydrochloric acid. The white precipitate thus obtained was digested by heating the suspension to boiling, after which the mixture was cooled and the precipitate was collected on a filter. After drying in vacuo the weight of the acid was 1.6 g. (79% of the theoretical amount, assuming the starting material to be diester); M. P. 253 C. (uncor.) with loss of carbon dioxide. One gram of this acid was decarboxylated to 4-hydroxy-7-chloroquinoline in accordance with the procedure described in the above identified Price, Roberts and Herbrandson application. The recrystallized product was found to be identical with an authentic sample of e-hydroxy-7-chloroquinoline.

Notes 1. m-Chloroaniline produced by the reaction was isolated from the dilute hydrochloric acid solution by neutralization with ammonium hydroxide and extraction of the alkaline. mixture with ether. The identity of the crude amine (ca. 2.6 g.) was proved by conversion to the benzene-sulfonamide; melting point of the unrecrystallized derivative, (118-119" C.). (Literature, 121 C.).

2. Any unchanged malonic ester is removed by distillation at reduced pressure.

3. Addition of more low boiling petroleum ether to the filtrate and further cooling produced an oil which crystallized on standing to yield 0.8 g. of crude yellow crystals.

EXAMPLE II Preparation of- 4,7-dichloroquin0line from MA!- Di-m-chlorophenylformamidine (a) PREPARATION OF THE DIES'IER N,N-Di-m-chlorophenylformamidine (79.5 g. 0.3 mole) and diethyl malonate (48 g., 0.3 mole) were heated with agitation for ten hours in a 200-cc. flask. The temperature of the reaction mixture was maintained at IOU- C. At the end of this time. the mixture was cooled and diluted with 500 cc. of benzene. The solution was agitated and, with external cooling, there was added 10 g. of filter cel and 30 cc. of concentrated hydrochloric acid. After agitating for fifteen minutes, the mixture was filtered through a 10-g. pad of filter cel. The filter cake was slurried with 125 cc. of benzene and filtered. The new cake (A) was washed with 50 cc. and then with 35 cc. of benzene. All the benzene solutions were combined.

(Zr) CYCLIZATIOAT AND HYDROLVYSIS Dowtherm (225 cc.) was added to the benzene solution and the mixture was distilled until the temperature of the reaction mixture reached 245 C. The downward condenser was replaced by a return air condenser and heating was continued with agitation for forty-five minutes at a temperature. of 245-250 C.

The mixture was cooled to 100 C., 450 cc. of 10% sodium hydroxide was'added, and hydrolysis was efiectedby refluxingwith agitation for three hours. At the end. of" this time, the aqueous phase was separated from the Dowtherm layertemperature 90-95 C.

The aqueous layer was allowed to cool to room temperature and then diluted to 1 liter. The solid anilide, 3-m-chlorocarbani1ido-4-hydroxy- 7-chloroquinoline which had precipitated, was recovered by filtration, washed with three 100-cc. portions ofwater which were added to the main filtrate, and dried at 110 C. It weighed 5.0 g. and melted at 308-313 C. (uncor.) This material can be hydrolyzed by means of 70% sulfuric acid to give 7-ch1oro-4-hydroxyquinoline3-carboxylic acid and m-chloroaniline.

The filtrate was made acid to Congo red with 50 B sulfuric acid. The 7-chloro-4-hydroxyquinoline-3-carboxylic acid (b), was isolated by filtration, washed with water until the washings were neutral, and dried at 110 C. It weighed 40 g. and melted with decomposition at 2 -248 C. (uncor.).

(c) 1Il-CHLOROANILINE RECOVERY The dried cake (A) containing formamidine hydrochloride and m-chloroaniline hydrochloride was refluxed with a mixture of 37 cc. of 50 B sulfuric acid and 1350 cc. of water for three hours. The mixture was cooled and made alkaline with 50 B sodium hydroxide and the m-chloroaniline was recovered by steam distillation. The oil which separated Weighed 29.8 g. Titration with standard sodium nitrate indicated the presence of an additional 11.4 g. of m-chloroaniline in the aqueous layer.

(cl) DECARBOXYLATION AND CONVERSION TO 4,7-

. DICHLOROQUINOLINE Dowtherm (280 cc.) was heated to 225-230 C. and, with agitation, 39.5 g. of the'7-chloro-4-hy droxyquinoline-3-carboxy1ic acid (b) was added over a forty-minute period. Heating at 225-280 C. was maintained until a homogeneous solution was obtained.

The mixture was cooled to 90 C. and 56 g. of phosphorus oxychloride was added. The mixture was agitated for one hour at 90-100C. Then, after cooling to C., 280 cc. of water was added. Rapid agitation was maintained for one hour while the temperature was kept at 15 C. The aqueous layer was separated and the Dowtherm layer was washed with 100' cc. of 50 B sulfuric acid.

The wash was combined with the main aqueous layer and the mixture was diluted to' 1 liter. The solution was clarified by agitation with 5 g. of filter cel followed by sludge filtration. The clear filtrate was made alkaline to Brilliant yellow with 50 B sodium hydroxide. The crude 4,7- dichloroquinoline was isolated by filtration, washed with three 100-cc. portions of water and dried in an oven at 50 C. It weighed 27.6 g. and melted at 75-80 C. (uncor.).

The crude dichloroquinoline was recrystallized from Skellysolve C. The first crop of crystals weighed 11.0 g. and melted at 82-85 C. The second crop weighed 6.8 g. and melted at 82-84= C. The third crop weighed 3.0 g. and melted at '79-82 C. The residue weighed 4.5 g. and melted at 59-66 C.

It may be of interest to point out the advantages of the present process as applied to the preparation of 7-chloro-4-hydroxyquinoline-3- carboxylic acid, as contrasted to certain limitations of the four best methods heretofore available for the production of this compound; namely, the procedures described in: (1) the Price, Roberts and Herbrandson application, Ser. No.

10 597,584, filed June 4, 1945 (Invention Disclosure OSRD-3834) (2) Snyder and Jones application, Ser. No. 597,586, filed June 4, 1945 (Invention Disclosure 0SRD3835) (3) Snyder and Jones application, SerfNo. 597,587, filed June 4,1945 (Invention Disclosure OSRD-BBSG) and (4) Price and Reitsema application, Ser. No. 597,585, filed June 4, 1945 (Invention DisclosureOSRD-3850). Considering these prior processes seriatim,the starting materials of the present, invention are much more economical and readily v,available than those heretofore required forcarryinglout the Price, Roberts and Herbrandson process, and

the over-all yield of 17 chloro-4-hy'droxyquinoline-3-carboxylic acidis better. The essential difference in raw materials isthe use of inexpensive, readily-available formic acid in place of ethyl orthoformate (which requiresv chloroform and sodium). The principal disadvantage in the cyclization of the anilide anils or the cyano anil s described in the two Snyder and Jones applications is the high dilution necessary for satisfactory yields. A second drawback is the he, cessity of acid rather than alkaline hydrolysis of the cyclized product, which introduces several operational difficulties. The new processof-the present invention yields a product that can be cyclized in better'yield at high concentrations, yielding a product which may be directlyihydrolyzed by alkali without filtration from the solvent used for cyclization. The advantages of the present process over that describedin the Price and Reitsema application are in the overall yield and the economy of starting materials.

The preparation of the starting material used" in the Price and Reitsema process requires dium and esters of acetic and formic acid. .The

condensation to form methyl formylacetate. gives yields reported in therange of -80% but its condensation with m-chloroaniline is somewhat diflicult to carry out and has notbeen onk;

plished in very good yields. It will then be apparent that the process ofthe presentinvention is characterized by a number of advantages over the most satisfactory methods heretofore, available for preparing substituted.-hydroxy-quinoline compounds.

We are aware of the fact that Dains et al., Jour. Amer. Chem. Soc, 35,- 970 (1913), extensively studied the interaction of diaryl formamidines of the type R-N=CH-NI-IR with various active methylene compounds of the type CH2(X) (Y), including malonic :rester, cyanoacetic ester and the like. These investigators postulated that in the case of malonic ester the reaction necessarily proceeded through the diester to the half ester, as indicated by the following scheme:

|- RNHZ] GOOR COOR

000?. (B) [RNHCH=C RNHa] COOR GOOR

RNHCH=C R'OH CONHR However, they pointed out that, although in the case of active methylene compounds other than malonic ester, first-stage reaction products could be isolated, in the case of malonic ester, "this secondary reaction seems always to occur. This observation suggested that in the case of malonic ester, the rate of the secondary reaction in this instance was too great to enable the isolation of the postulated intermediate. It will be evident that the process of the present invention isbased upon the discovery of the critical reaction condition necessary to enable the isolation in good'yields of a compound that has heretofore 'merely been postulated as a necessary but transitory intermediate.

In the above described specific examples the process of the present invention was illustrated by its application to the preparation of ethyld-carbethoxy-flm-chloroanilinoacrylate and the conversion of the latter to 7-chloro-4-hydroxyquinoline-3-carboxylic acid. However, the principles involved are broadly applicable to the interaction of malonic esters with diarylformamidines, generally, including those wherein the aryl nuclei of the formamidine comprises, for instance, a substituted phenyl radical having substituents such as alkyl (e. g., methyl, etc.), alkoxy (e. g., methoxy, ethoxy, etc.), aryloxy (e. g., phenoxy, etc.), benzo, carbalkoxy (e. g., carbethoxy), cyano, nitro and the like. In addition, it is evident that cyclization media other than diphenyl ether may be used if desired; for example, other high boiling solvents or heat exchange media such as high boiling hydrocarbons may be used to carry out this step, or indeed the solvent may be dispensed with entirely.

Many other variations, modifications and extensions of the principles illustrated in the foregoing specific examples will be apparent to those skilled in the art. We therefore intend to be limited only in accordance with the appended patent claims. This application is a division of our copending application Serial Number 651,432, filedMarch l, 1946 for Method of Manufacturing Certain Basic Compounds.

Having thus described our invention, what we claim as new and wish to secure by Letters Patent is:

l. A method of producing arylaminomethylene malonic esters selected from the group consisting of compounds of the type ArNHCH :C (000R) 2 and their isomeric anils ArN=CHCH (COOR) which comprises heating a reaction mixture containing approximately equimolar proportions of a malonc ester of the type CHz(COOR)2 and a diarylformamidine of the type to a temperature between about 100 C. to about 125 C. for a period of about two hours to about six hours, thereby producing a substantial proportion of said arylaminomethylene malonic ester but insufficient to produce a substantial proportion of the amide-ester derivative of said malonic ester; the R group in the foregoing formulae representing a lower alkyl radical and the Ar group a monocyclic aryl radical.

2. The method of claim 1 wherein said diarylformamidine comprises a formamidine oi the where X is a monovalent halogen nuclear substituent.

3. The method of claim 1 wherein the reaction mixture resulting from said heating step is mixed with aqueous hydrochloric acid and a water-immiscible solvent for the desired arylaminomethylene malonic ester, after which th resulting non-aqueous solution in said water-immiscible solvent is separated from the aqueous solution and also from any undissolved solid material.

4. The method of claim 1 wherein the reaction mixture resulting from said heating step is mixed with aqueous hydrochloric acid and a volatile, water-immiscible solvent for the desired arylaminomethylene malonic ester, after which the resulting, non-aqueous solution in said water-immiscible solvent is separated from the aqueous solution and also from any undissolved solid material, and the volatile components of said sepa rated non-aqueous solution are separated from the solute.

CHARLES C. PRICE. ROYSTON M. ROBERTS.

REFERENCES CITED The following references are of record in the file of this patent:

Beilstein, Handbuch Der Organischen Chemie, Vierte Aufiage, vol. 13, page 532. 

1. A METHOD OF PRODUCING ARYLAMINOMETHYLENE MALONIC ESTERS SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS OF THE TYPE 